1. Field of the Invention
The present invention relates to an input device provided with strain gages to be used in combination with a computer or the like.
2. Description of the Related Art
Referring to FIG. 13, a conventional input device provided with strain gages has control member 51, formed of a flexible synthetic resin and having an operating part 51a formed in a shape resembling a rectangular a solid, three planar base parts, i.e., a first base part 51b, a second base part 51c and a third base part 51d, extending under the operating part 51a at right angles to each other, and a joining part 51e underlying the operating part 51a and joining together the planar base parts 51b, 51c and 51d. The control member 51 is mounted on a frame member 50 of a keyboard combined with a computer with the lower surfaces of the base parts 51b, 51c and 51d in contact with the frame member 50, and with the free ends of the base parts 51b, 51c and 51d pressed against the frame member 50.
When operating part 51a of the control member 51 is tilted in directions X1, X2, Y1 or Y2, the base parts 51b, 51c and 51d are warped. Strains of the base parts 51b, 51c and 51d vary according to the inclination of the operating part 51a. 
A first strain gage 53 and a second strain gage 54 having resistors, and leads 55, 56 formed by printing a conductive ink containing silver and connected to the strain gages 53 and 54 are placed on one surface of a flexible wiring board 52.
A portion of the other surface of the flexible wiring board 52 opposite the surface on which the strain gages 53 and 54 are placed is bonded to upper surfaces of the base parts 51b and 51c extending at right angles to each other with an adhesive. The strain gages 53 and 54 are attached to the base part 51b and the 51c, respectively.
When the operating part 51a of the control member 51 is tilted in the direction X1, the first base part 51b is warped so that the upper surface thereof is stretched. Consequently, the first strain gage 53 attached to the upper surface of the first base part 51b is stretched and its electrical resistance increases. When the operating part 51a is tilted in the direction X2, the first strain gage 53 attached to the upper surface of the first base part 51b is compressed together with the upper surface of the first base part 51b and its electrical resistance decreases. Similarly, the electrical resistance of the second strain gage 54 increases when the operating part 51a is tilted in the direction Y1 and the same decreases when the operating part 51a is tilted in the direction Y2. Changes in the electrical resistances of the strain gages 53 and 54 are converted into voltage changes, the voltage changes are read by a computer, and the computer controls a cursor for movement in vertical and horizontal directions according to the tilting direction of the operating part 51a, i.e., the directions X1, X2, Y1 and Y2.
Since the lower surfaces of the base parts 51b, 51c and 51d of the control member are entirely in contact with the frame member 50, the base parts 51b and 51c cannot be greatly warped and, the operation of the input device is not satisfactory. Base end parts of the base parts 51b and 51c of the operating part 51a are joined to the joining part 51e. Therefore, the second base part 51c and the strain gage 54 attached thereto, which should not be strained, are nevertheless strained through the joining part 51e by the turning of the operating part 51a in the directions X1 and X2 to strain the strain gage 53 attached to the first base part 51b. Similarly, the first base part 51b and the strain gage 53 attached thereto, which should not be strained, are nevertheless strained through the joining part 51e by the turning of the operating part 51a in the directions Y1 and Y2 to strain the strain gage 54 attached to the second base part 51c. Thus, the strain gages 53 and 54 are strained and the electrical resistances thereof changes greatly when the same should not be strained.
Since a restriction on the position of the base parts 51b, 51c and 51d on the frame member 50 sets limits to the lengths of the base parts 51b, 51c and 51d of the control member 51 because the free end parts of is attached to the frame member 50, the first base part 51b and the second base part 51c have different lengths, respectively. Consequently, the strain gages 53 and 54 differ greatly from each other in the changing mode of resistance and the functions of the strain gages 53 and 54 do not correspond accurately to the operation of the control member 51. Since the base parts 51b, 51c and 51d are attached to the frame member 50, the operation of the keyboard affects the condition of the base parts 51b, 51c and 51d and causes the cursor to move.
Accordingly, it is an object of the present invention to provide an input device provided with strain gages and capable of accurately controlling a cursor displayed on a display controlled by a computer.
According to a first aspect of the present invention, an input device comprises: a control member having an operating part, and a planar base part having a portion connected to the operating part and extending in a plane perpendicular to the axis of the operating part; strain gages placed on an upper surface of the base part; and a planar holding member holding the control member; wherein the base part has a plurality of arms having end portions connected to the operating part and extending at an angle of 90xc2x0 to each other in a plane perpendicular to the axis of the operating part, and connecting parts connecting the adjacent arms. The connecting parts or the holding member is provided with projections to secure spaces between the arms provided with the strain gages, and the holding member, and the control member is held on the holding member.
Preferably, the projections are formed on the connecting parts so as to be in contact with the holding member to secure the spaces between the arms and the holding member.
Preferably, the arms are arranged in a cross-shaped arrangement.
Preferably, the base part has openings defined by the adjacent arms and the connecting parts.
Preferably, the connecting parts of the control member are fastened to the holding member.
Preferably, the holding member has a holding part on which the base part of the control member is mounted, and arms extending from the holding part, and the arms are provided with support portions having a bending strength greater than that of the holding part.
Preferably, the holding member is formed by shaping a metal plate, and the support parts are formed by folding up portions of the metal plate.
According to a second aspect of the present invention, an input device comprises: a control member having an operating part, and a planar base part having a portion connected to the operating part and extending in a plane perpendicular to the axis of the operating part; strain gages placed on an upper surface of the base part; and a holding member holding the control member; wherein the base part has a plurality of arms having inner end portions connected to the operating part and extending at an angle of 90xc2x0 to each other in a plane perpendicular to the axis of the operating part, and connecting parts connecting the adjacent arms; the strain gages are placed on the arms; and the connecting parts are fastened to the holding member.
The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which:
FIG. 1 is a plan view of an input device in a preferred embodiment according to the present invention;
FIG. 2 is a sectional view taken on line 2xe2x80x942 in FIG. 1;
FIG. 3 is a sectional view taken on line 3xe2x80x943 in FIG. 1;
FIG. 4 is a plan view of the input device shown in FIG. 1, in which a shielding plate is removed;
FIG. 5 is an exploded perspective view of the input device shown in FIG. 1;
FIG. 6 is a plan view of a support member included in the input device shown in FIG. 1;
FIG. 7 is a side elevation of the support member shown in FIG. 6;
FIG. 8 is a plan view of a blank for forming the support member;
FIG. 9 is a plan view of a control member included in the input device shown in FIG. 1;
FIG. 10 is a sectional view taken on line 10xe2x80x9410 in FIG. 9;
FIG. 11 is a plan view of an input device in another embodiment according to the present invention;
FIG. 12 is a sectional view taken online 12xe2x80x9412 in FIG. 11 and
FIG. 13 is a perspective view of a conventional input device.